Utilization of mixtures of organic and inorganic acids in the preparation of greases



UTILIZATION OF MIXTURES OF ORGANIC AND IfiiglggglgllC ACIDS IN THEPREPARATION OF Arnold J. Morway, Clark, N. J., assignor to Esso Researchand Engineering Company, a corporation of Delaware No Drawing.Application November 30, 1955 Serial No. 550,176

9 Claims. (Cl. 25236) This invention relates to lubricating greasecompositions, and more particularly to lubricating oil thickened togrease consistency with neutralized blends or mixtures of low molecularweight carboxylic acids and mineral acids and stabilized with a minoramount of an aluminum soap of a high molecular weight carboxylic acid.

In brief, this invention pertains to the stabilization of lubricatinggrease compositions containing as the thickening agent an alkaline earthmetal neutralized blend of a low molecular weight carboxylic acid, e. g.acetic acid, with a strong inorganic acid, e. g. phosphoric acid, and analuminum soap of a high molecular weight fatty acid, e. g. aluminumstearate.

When the metal salts of low molecular weight carboxylic acids aredispersed in lubricating oils, the reacid in lubricating greasecompositions containing large amounts of metal soaps as the thickeningagent has previously been suggested in the art. In U. S. Patent No.2,513,680 to Schott and Armstrong, for example, less than about 2.0% byweight of calcium phosphate is employed to improve the skin hardeningand storage stability properties of calcium base greases.

It has now been found that a large amount of a mineral acid incombination with a low molecular weight carboxylic acid can effectivelythicken a lubricating oil to grease consistency provided that a minoramount of aluminum soap of a high molecular weight acid is employed inconjunction therewith. The aluminum soap appears to prevent the greasecomposition from separating oil during storage over long periods of timeand to prevent the thickening agent from agglomerating and settling outof the lubricating composition.

It is not known what reactions the strong inorganic acid enters intoduring the grease preparation method of this invention. When nitric acidis employed, for example, the resulting grease composition had adistinctive red color, as hereinafter shown. However, for the purposesof this invention it is suificient to note that lubricating compositionsencompassed therein are prepared by utilizing blends or mixtures of thelow molecular weight carboxylic acids and mineral acids.

Suitable low molecular weight carboxylic acids include saturated andunsaturated aliphatic carboxylic acids having from about 1 to about 3carbon atoms per molecule such as formic acid, acetic acid, propionicacid, etc. Acetic acid is the preferred low molecular weight carboxylicacid of this invention and may be either glacial acetic acid or anaqueous solution thereof, the concentration of the acetic acid in theaqueous solution varying from about 60 to 99.9 wt. percent. Substitutedacetic acids having two carbon atoms per molecule such as chloro-acetic'acid, glycolic acid, thioglycolic acid, glycine, etc. may also be usedto modify the structure of lubricating compositions made in accordancewith this invention. The amount of low molecular weight carboxylic acidemployed will be within the range of about 5 to 20 wt. percent,preferably about 10 to 15 wt. percent, based on the total lubricatingcomposition.

The mineral acids which may be employed in this invention includephosphoric acid, nitric acid, sulphuric acid, hydrochloric acid andmixtures of any combination of these acids. The concentrations of themineral acids may vary from about 5% to 100%. The strong inorganic acidsare utilized in amounts ranging from about 3 to 15 wt. percent,preferably about 5 to 10 wt. percent, based on the total lubricatingcomposition.

The stabilizing agent of this invention is an aluminum soap of a highmolecular weight carboxylic acid having from about 16 to 22 carbon atomsper molecule. Aluminum stearate is preferred, though soaps of palmiticacid, arachidic acid, behenic acid, etc. may also be employed tostabilize the lubricating grease compositions of this invention. Onlystabilizing proportions of the aluminum soap of from about 2 to 10 wt.percent, preferably about 3 to 6 wt. percent, based on the totallubricating composition, need be used.

Suitable metal bases for neutralizing the blends of low molecular weightcarboxylic acids and mineralacids include the alkaline earth metals:calcium, barium, magnesium and strontium; and the alkali metals: sodium,potassium and lithium. The alkaline earth metals are preferred, andcalcium is especially preferred. Ordinarily, the grease-making processof this invention will utilize from about 10 to 20 wt. percent based onthe total lubricating composition, of the metal hydroxide or carbonate.Mixtures of the above metals may also be employed, if desired.

The lubricating oils employed as the menstrua of the lubricatingcompositions of this invention may be either conventional grease-makingmineral oils or synthetic lubricating oils. In general, the mineral andsynthetic lubricating oils should have a viscosity within the range ofabout 50 to 2000 S. U. S. at 100 F. and about 30 to 200 S. U. S. at 210'R, an ASTM pour point of about +20 to F., a flash point of about 350 to650 F., and a viscosity index of about 0 to 60, although lubricatingoils having a viscosity index; of or higher can also be employed. When astrong acid like nitric or sulphuric is used in high concentrationsaccording to the present invention, the preferred menstrum is a minerallubricating oil.

The synthetic lubricating oils include esters of monobasic acids (e; g.an ester of C alcohol with C OX0 acid, an ester of C 0x0 alcohol withoctanoic acid, etc.), esters of dibasic acids (e. g. di-Z-ethyl hexylsebacate, dinonyl adipate, etc.), esters of glycols (e. g. C Oxo aciddiester o-f tetraethylene glycol, etc), complex esters (e. g. thecomplex ester formed by reacting one mole of tetraethylene glycol withtwo moles of sesacic acid and two moles of Z-ethyI-hexanol, a complexester formed by reacting one mole of azelaic acid, one mole oftetraethylene glycol, one mole of C Oxo alcohol and one mole of C Oxoacid), esters of phosphoric acid (e. g. the ester formed by contactingthree moles of the mono-methyl ether of ethylene glycol with one mole ofphosphorous oxychloride, etc.), halocarbon oils (e. g. the polymer ofPatented Dec. 16, 1958 chlorotrifluoroethylene containing twelverecurring units of chlorotrifluoroethylene), alkyl silicates (e. g.methyl polysiloxanes, ethyl polysiloxanes, methyl-phenyl polysiloxanes,etc.), sulfite esters (e. g. ester formed by reacting one mole of sulfuroxychloride with two moles of the methyl ether of ethylene glycol,etc.), carbonates (e. gather carbonateformed by reacting C Oxo alcohol.with ethyl carbonate to form a half ester and reacting this .half esterwith tetraethylene glycol), mercaptals (e. g. the mercaptal formed byreacting Z-ethyl hexyl mercap'tan with formaldehyde), formals (e. g. theformal formed by reacting C OX alcohol with formaldehyde), .polyglycoltype synthetic oils (e. g. the compounds formed by condensing butylalcohol with fourteen units .of propylene. oxide, etc.), or mixtures ofthe above in any proportions.

The lubricating compositions of the invention will con- :tain about 50.to 90 wt. percent, preferably about 60 to -80.wt..percent, of. themineral .and/or synthetic lubricating oil and about 10 to 50 wt.percent, preferably about -20 to 40 .wt. percent of the reactionproducts of blends .ofithcabove acids with the metal base plus thealuminum .soap.

lngeneral, the lubricating grease compositions of this :invention may beprepared by coneutralization of a blend immediately.

The preferred method for preparing the lubricating compositions of theinvention involves dispersing the .aluminum soa in the lubricating oilat a temperature of -from about 270 to 350 F. with stirring. Theresulting dispersion is cooled to room temperature, preferably by pancooling. The .cold aluminumsoap-lubricating oil dispersion is thencharged to a grease kettle equipped with means for efficient stirring.The metal hydroxide is .added with stirring to obtain a smooth uniformslurry.

The low molecular Weight carboxylic acid blended with t the mineral acidis then added to the grease kettle with stirring. A solid grease formsalmost immediately withoutthe application of external heat. Stirring iscontinued until the temperature subsides from about 180 to 210 F. toabout 100 to 140 F. The resulting grease composition may be finished bypassage through a Morehouse .mill or Gaulin homogenizer at high rates ofshear.

Only a portion of the total lubricating oil required to prepare thecompositions of this invention need be initially employed to dispersethe aluminum soap and the blend of acids. The remainder of thelubricating oil can be conveniently added subsequent to the addition ofthe blend of low molecular weight carboxylic acids and mineral acids.

When a portion of the lubricating oil is a saponifiable synthetic oil,it is preferred to initially disperse the reactants in a mineral oil orthe non-saponifiable synthetic or] portion of the lubricating oil, andto then add the .saponifiable synthetic oil to the grease batch afterthe latter has been cooled.

Conventional lubricating grease additives may also be employed in thelubricating compositions of the present invention. These additives, forexample, include: oxida .tion inhibitors, such as phenyl alphanaphthylamine, cor

rosion inhibitors such as sorbitan monooleate, tackiness agents such aspolyisobutene or high molecular weight polymerized acrylic esters,load-carrying compounds such as sulfurized and/or phosphorous and/orchlorine containing oil-soluble materials, and the like.

The invention will be more fully understood by reference to thefollowing specific examples. illustrating various modifications of theinvention.

. 4 EXAMPLE I A lubricating grease composition according to thisinvention was prepared from the following constituents:

Formulation: Percent weight Glacial acetic acid 14.0 Phosphoric acidconc.) 6.0 Hydrated lime 15.0 Aluminum stearate 3.2 Phenyl alphanaphthylamine 0.5 Mineral lubricating oil 55 SUS 210 F 61.3

Preparation The aluminum stearate was dispersed in all of the minerallubricating oil by heating to a temperature of about 300 F. withstirring. The resulting dispersion was cooled to room temperature inpans. Just prior to drawing into the pans, the phenyl alphanaphthylamine was added to the dispersion. The cooled dispersion wasthen charged to a grease kettle, and the lime added with mixing toobtain a smooth uniform slurry. A blend of the acetic acid and thephosphoric acid was then charged to the grease kettle. Without heatingthe resulting grease batch, the temperature rose to about 190 F.Stirring was continued until the temperature subsided, and the greasewas finished by being passed through a Gaulin homogenizer.

, Properties Excellent, smooth uniform grease.

Appearance Droooinz point, F... Penetration 77 F. mirth/10:

Unworked Worked on strokes 210.

Worked 70,000 strokes- 235. Water solu ility Nil.

-. Excellent.

After removal of water, crease becomes somewhat softer but does not losestructure.

Norma Hoffman oxidation test 335.

(hrs. to 5 n. s. 1. drop). Lubrication lite (hours) (250, F. 1000+.

Water renellency 11). Phase changes up to 400-F EXAMPLE II Formulation:Percent weight Glacial acetic acid 14.0 Nitric acid (70% cone.) ....1 -48.6 Hydrated lime 15.1 Aluminum stearate 3.1 Phenyl alpha naphthylamine0.6 Mineral lubricating oil 55 SUS @210 F 58.6

Preparation Similar to thatdescribed in Example I, except that nitricacid was employed in place of the phosphoric acid.

Properties Appearance Excellent. smooth uniform red product.

Pen trations, 77 F., mmJlO:

Unworked 200.

Worked 60 St nkes..

Worked 70,000 strokes Semi-fluid Dro ping p int, F 400+. Watersolubility (boilin wato No turbidity afte 10 minutes boiling. Phasechanges up to 400 F. Grease softens after removal o water but does notlose structure. Semi {luld on cooling to room temperaure. Norma Hofimauoxidation test 250.

(hrs. to 5 p. s. i. drop). Lubri ation lile (hours) (250 F. 850. 10,000R. P.

The above data shows that mineral acids other than phosphoric acid canbe effectively employed to prepare lubricating grease compositions incombination with low molecular weight carboxylic acids. It will befurther noted that when nitric acid is employed, the resulting greasecomposition had a red color indicating that this strong inorganic acidmay have reacted in some manner with the lubricating oil base.

It will be further understood that the present invention is notnecessarily limited to the specific materials and conditions of theforegoing examples. These materials and conditions may be varied withinthe limits indicated in the general portions of the specification.

What is claimed is:

l. A lubricating composition comprising a major amount of a lubricatingoil, and an alkaline earth metal neutralized blend of 5 to 20 wt.percent low molecular weight carboxylic acid having from about 1 to 3carbon atoms per molecule and 3 to 15 wt. percent mineral acid, and 3 to6 wt. percent aluminum soap, all of said weight percentages being basedon the total weight of the lubricating composition.

2. The lubricating composition of claim 1 wherein said lubricating oilis a mineral lubricating oil.

3. The lubricating composition of claim 1 wherein said alkaline earthmetal is calcium.

4. The lubricating composition of claim 1 wherein said mineral acid isselected from the group consisting of phosphoric acid, nitric acid,hydrochloric acid, sulfuric acid, and mixtures thereof.

5. The lubricating composition of claim 1 wherein said aluminum soap isan aluminum soap of a high molecular weight carboxylic acid having fromabout 16 to 22 carbon atoms per molecule.

6. The method of preparing a lubricating grease composition whichconsists essentially of dispersing an aluminum soap of a high molecularweight carboxylic acid having from about 16 to 22 carbon atoms permolecule in a lubricating oil by heating, cooling said dispersion toambient temperature, adding an alkaline earth metal hydroxide to saidcooled dispersion, then adding a blend of a low molecular weightcarboxylic acid having from about 1 to 3 carbon atoms per molecule and amineral acid to the resulting mixture to obtain said lubricating greasecomposition.

7. The method of claim 6 wherein said aluminum soap is aluminumstearate.

8. The method of claim 6 wherein said low molecular weight carboxylicacid is acetic acid.

9. The method of claim 6 wherein said mineral acid is nitric acid.

References Cited in the file of this patent UNITED STATES PATENTS2,417,429 McLennan Mar. 18, 1947

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR AMOUNT OF A LUBRICATINGOIL, AND AN ALKALINE EARTH METAL NEUTRALIZED BLEND OF 5 TO 20 WT.PERCENT LOW MOLECULAR WEIGHT CARBOXYLIC ACID HAVING FROM ABOUT 1 TO 3CARBON ATOMS PER MOLECULE AND 3 TO 15 WT. PERCENT MINERAL ACID, AND 3 TO6 WT. PERCENT ALUMINUM SOAP, ALL OF SAID WEIGHT PERCENTAGES BEING BASEDON THE TOTAL WEIGHT OF THE LUBRICATING COMPOSITION.